How To Repressurise Combi Boiler?

How To Repressurise Combi Boiler

Do you want to know how to repressurise combi boiler? The most common reason for this is because air got into the system and needs to be removed.

Repressurizing a combi boiler means opening up all of the faucets in your home and allowing water to flow out, then turning on each one again to force air bubbles out of the pipes. This should only take about ten minutes or so. If you’re doing it right, there will also be a noticeable hissing noise coming from your plumbing fixtures as they fill with hot water.

Once you’ve done this, please turn off all of your faucets except for one at first–usually whichever one you need hot water from–and test it by running cold water through it until it gets warm. Then, turn on all of your faucets and test each one until they’re all working properly.

After this, please turn off the tap you used to bleed the system and fill it back up with water.

The most important thing to keep in mind is that whatever small amount of air managed to get into your plumbing won’t just go away on its own. It has to be purged out of your system, and this is how you do it. If you turn on your faucets without removing the air, then opening up all of them at once will cause the water pressure to fluctuate wildly–and that can damage fixtures or equipment if done too often or too quickly.

As a rule of thumb, always turn on the faucets in your home in order from one o’clock to ten o’clock until all of them are open before closing them off again. This will allow you to know that they’re each bled properly, and it will prevent any pressure surges which might damage your equipment.

What is a combi boiler?

combi boiler is a water heater with both a hot-water tank and an electric heating element. The boiler heats the water in the tank, which then circulates through pipes to provide hot water for both space heating and domestic purposes.

How To Repressurise Combi Boiler?

Repressurizing the combi boiler is fairly simple to do. There are quite a few steps, but all of them are easy to follow. First, turn off the water supply to the home or that particular area where you need hot water. Leave one tap slightly open, so any air bubbles have somewhere to escape from.

Next, pump air into the hot-water system by opening one tap until it’s hard to pull up any more air. When you feel the water has reached max pressure, shut off the tap and let it fill up for about 10 seconds.

After 10 seconds, close that tap and turn on other taps in your house that need hot water. Turn on other taps in your house that need hot water.

What are two reasons for an airlock in the system?

There are several reasons for this problem. If you’re taking a lot of showers, you could be introducing too much air into the system through your hot-water tank. Try to limit showering when you know there’s not much water pressure in the system. This can also happen if it’s been a long time since the boiler was last used. If this is the case, you can also try to run some water through it for about 10 minutes to eliminate any air buildup.

What do you need for this project?

For this project, all you need is an extender rod and some masking tape. It’s also a good idea to have some Teflon tape on hand. These are all cheap and easily accessible tools that should be able to get the job done. Some people might even want to use gloves, especially if it’s been a long time since the boiler was used last. The masking tape can help with removing any excess water that comes out of the extender rod.

How long does it take to repressurise a combi boiler?

It’s pretty quick and easy to do, usually about five minutes or less. Just make sure you don’t leave any water dripping anywhere, as this could cause damage to your home. It can also stain walls and furniture.

How much does it cost to repressurise a combi boiler in the UK

To repressurise a combi boiler in the UK cost around £15 to £20. This is for the parts needed, not the actual labour. Repressurising a combi boiler is usually cheaper than repairing a regular boiler system because it doesn’t require any major work on the boiler itself. It’s all in keeping air out of your system and purging old water from your tank.

Why would you need to repressurise your combi boiler?

If you have been experiencing problems with your combi boiler, the chances are that it needs repressurising. It’s a common problem, and one of the most frequently asked questions is, “why do I need to pressurise my combi boiler?” The answer is simple, really – because air has got in. All you have to do is take out the air from the system so that hot water will flow freely again.

How does this happen?

There are many different reasons for this happening, but one of them which can be easily avoided and quite common is when someone leaves their tap running after they’ve finished using it. When people turn off their taps but don’t wait for any water to come out before leaving the tap running, it creates a vacuum in the pipe. This, combined with the pressure created by the boiler, results in the air getting into the system through any open taps.

What’s wrong with air getting into my combi boiler?

There are only two problems that can go wrong when air gets into your combi boiler: hot water will not flow, and the boiler’s pump will be worn out sooner than expected. Because air cannot be compressed, it cannot be pushed around through the system as water does, so it gets stuck instead.

This means that your thermostat won’t switch on when it should, causing you to have no hot water at all. The other problem which could arise is the boiler’s pump overheating and burning out. When the thermostat detects high water temperature, it sends an electric signal to the pump to switch on and remove this hot water from your heating system.

If there isn’t any, then the pump will overheat and burn out – leaving you with a pretty hefty bill for a new one! The same thing can happen if the pump is running, but there are no cold water pipes to push through.

How To Repressurise Combi Boiler

Common mistakes when trying to repressurise a combi boiler

There are many mistakes that you can make when trying to repressurise a combi boiler, and we’re going to go through some of the most common ones so that you know what NOT to do.

Shutting off your hot water taps without waiting for the water to flow out:

The most common mistake people make when they turn off their tap but don’t wait for any water to come out before leaving the tap running creates a vacuum in the pipe. This, combined with the pressure created by the boiler itself, results in the air getting into the system through any open taps.

Leaving taps on too long: 

Leaving taps on for an extended period can lead to them becoming stuck or might result in some leakage. This can cause the system to become pressurised or even unpressurised, leading to the problems mentioned above.

Turning on taps just before turning off the boiler:

If you turn your heating on with no hot water in your system, then – as you would expect – nothing will come out of any of your taps. Here’s where it gets interesting: if the system isn’t pressurised and you shut off your boiler, then as soon as it gets to normal working temperature, the thermostat will switch the pump on.

If there is no water in the system, however, then this means that it will burn out as before!

What are some signs that indicate I should repressurise my system?

You should repressurise your system if you have been experiencing problems with your combi boiler. One of the most common reasons for this is because air got into the system and needs to be removed. If you witness that your combi boiler is not working properly or notice hot water disappearing at an abnormal rate, then it is possible that air has gotten into your system and needs to be removed. If only one tap isn’t giving hot water, or if none of them is – run the taps for a minute or two before turning off the boiler.

How To Repressurise a Baxi combi boiler?

To repressurise a Baxi combi boiler, you need to get new water from the hot water tank. Turn off the heating system and open the taps on all of the radiators. Open a fresh hot tap and make sure it doesn’t flow, then turn on the heating. Run this tap for about five minutes before opening another radiator nearest to it.

When all of the radiators in the property have been opened and warmed up, and there is still no hot water, turn off the heating and reconnect it to your mains supply, then switch on your boiler and wait for it to reach temperature.

Baxi combi boilers also sometimes need an extra step and turn the heating on and off to ensure that they are fully repressurised. You need to turn off your hot water tank and run a tap from it for five minutes.

When you have done this, leave the pump on so the system can build-up ahead of pressure again before you turn it off and reconnect it to your heating.

Now you can turn on the heating and reach temperature before re-opening the radiators to get hot water flowing again. If this doesn’t work, call a professional engineer to look at your system for you.


Repressurizing a boiler system can be done with little effort. The key is to identify the cause of the pressure loss and then fix it. This article provides simple steps to repressurise any combi boiler, no matter what type or brand you have. If your water hasn’t been running hot for some time now, take these easy steps first before calling an engineer out to see if they need more information about your system’s air leakage.

References : What to do if your boiler loses pressure

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